Unit 14: Applications of Organic Chemistry
Learning aim D: Investigate organic chemistry reactions in order to gain skills in
preparative organic chemistry.
Assignment title:Making designer chemicals
P5- Carry out practical examinations of organic reactions safely in order to produce
predicted products.
P6- Explain the chemical reactions carried out in terms of the functional groups and
reaction conditions involved
1. Preparation of a compound without a carbonyl functional group
Introduction –
Making halogenoalkanes from alcohols using hydrogen halides
The general reaction looks like this:
Making chloroalkanes
It is possible to make tertiary chloroalkanes successfully from the corresponding alcohol and
concentrated hydrochloric acid, however to make primary or secondary ones you really need
to use a different method - the reaction rates are too slow.
A tertiary chloroalkane can be made by shaking the corresponding alcohol with concentrated
hydrochloric acid at room temperature.
Making bromoalkenes –
Instead of using hydrobromic acid, you usually treat the alcohol with a mixture of sodium or
potassium bromide and concentrated sulphuric acid. This produces hydrogen bromide which
reacts with the alcohol. The mixture is warmed to distil off the bromoalkene.
Making iodoalkanes –
In this case the alcohol is reacted with a mixture of sodium or potassium iodide and
concentrated phosphoric(V) acid, H3PO4, and the iodoalkane is distilled off. The mixture of
the iodide and phosphoric(V) acid produces hydrogen iodide which reacts with the alcohol.
Phosphoric(V) acid is used instead of concentrated sulphuric acid because sulphuric acid
oxidises iodide ions to iodine and produces hardly any hydrogen iodide. A similar thing
, happens to some extent with bromide ions in the preparation of bromoalkanes, but not
enough to get in the way of the main reaction.
Making halogenoalkanes from alcohols using phosphorus halides –
Making chloroalkanes -
Chloroalkanes can be made by reacting an alcohol with liquid phosphorus (III) chloride,
PCl3.
They can also be made by adding solid phosphorus(V) chloride, PCl5 to an alcohol.
This reaction is violent at room temperature, producing clouds of hydrogen chloride gas. It
isn't a good choice as a way of making halogenoalkanes, although it is used as a test for -OH
groups in organic chemistry.
There are also side reactions involving the POCl3 reacting with the alcohol.
Risk assessment -
Level of risk - Hazard - Precautions -
Low - if there is any hair that is out Hair should always betide up
or untucked clothing it could during a practical and clothes
come in contact with should always be tucked in
chemicals and cause whilst waring a lab coat as
problems. well.
Medium - Ethanol is highly flammable Flammable material should
when in contact with be kept away from ethanol to
flammable materials. prevent any fire in the area of
the practical.
High - Phosphorus (III) bromide Wear protective gloves when
(phosphorus tribromide is handling phosphorus
very corrosive the vapour tribromide. Also wear a face
will hydrolyse in the mask to avoid breathing in
moisture in air to give HBr. the chemicals. Wear goggles
throughout. Work in a fume
cupboard
Apparatus - Justification =
Test tubes Needed to but chemicals into.
Test tube rack Required so that test tubes can be kept
upright during the practical.
Measuring cylinder 10 cm3 Will be used to measure the volume of
chemicals used.
2 dropping pipettes Needed to transfer chemicals to different
places.
Learning aim D: Investigate organic chemistry reactions in order to gain skills in
preparative organic chemistry.
Assignment title:Making designer chemicals
P5- Carry out practical examinations of organic reactions safely in order to produce
predicted products.
P6- Explain the chemical reactions carried out in terms of the functional groups and
reaction conditions involved
1. Preparation of a compound without a carbonyl functional group
Introduction –
Making halogenoalkanes from alcohols using hydrogen halides
The general reaction looks like this:
Making chloroalkanes
It is possible to make tertiary chloroalkanes successfully from the corresponding alcohol and
concentrated hydrochloric acid, however to make primary or secondary ones you really need
to use a different method - the reaction rates are too slow.
A tertiary chloroalkane can be made by shaking the corresponding alcohol with concentrated
hydrochloric acid at room temperature.
Making bromoalkenes –
Instead of using hydrobromic acid, you usually treat the alcohol with a mixture of sodium or
potassium bromide and concentrated sulphuric acid. This produces hydrogen bromide which
reacts with the alcohol. The mixture is warmed to distil off the bromoalkene.
Making iodoalkanes –
In this case the alcohol is reacted with a mixture of sodium or potassium iodide and
concentrated phosphoric(V) acid, H3PO4, and the iodoalkane is distilled off. The mixture of
the iodide and phosphoric(V) acid produces hydrogen iodide which reacts with the alcohol.
Phosphoric(V) acid is used instead of concentrated sulphuric acid because sulphuric acid
oxidises iodide ions to iodine and produces hardly any hydrogen iodide. A similar thing
, happens to some extent with bromide ions in the preparation of bromoalkanes, but not
enough to get in the way of the main reaction.
Making halogenoalkanes from alcohols using phosphorus halides –
Making chloroalkanes -
Chloroalkanes can be made by reacting an alcohol with liquid phosphorus (III) chloride,
PCl3.
They can also be made by adding solid phosphorus(V) chloride, PCl5 to an alcohol.
This reaction is violent at room temperature, producing clouds of hydrogen chloride gas. It
isn't a good choice as a way of making halogenoalkanes, although it is used as a test for -OH
groups in organic chemistry.
There are also side reactions involving the POCl3 reacting with the alcohol.
Risk assessment -
Level of risk - Hazard - Precautions -
Low - if there is any hair that is out Hair should always betide up
or untucked clothing it could during a practical and clothes
come in contact with should always be tucked in
chemicals and cause whilst waring a lab coat as
problems. well.
Medium - Ethanol is highly flammable Flammable material should
when in contact with be kept away from ethanol to
flammable materials. prevent any fire in the area of
the practical.
High - Phosphorus (III) bromide Wear protective gloves when
(phosphorus tribromide is handling phosphorus
very corrosive the vapour tribromide. Also wear a face
will hydrolyse in the mask to avoid breathing in
moisture in air to give HBr. the chemicals. Wear goggles
throughout. Work in a fume
cupboard
Apparatus - Justification =
Test tubes Needed to but chemicals into.
Test tube rack Required so that test tubes can be kept
upright during the practical.
Measuring cylinder 10 cm3 Will be used to measure the volume of
chemicals used.
2 dropping pipettes Needed to transfer chemicals to different
places.
